The Cabinet minister was confronted by senior backbencher Nicky Morgan during heated exchanges in the Commons.
She said she and her allies were ready to vote with Labour against the crucial EU Withdrawal Bill unless ministers legally commit to parliamentary votes on any deal.
Urging ministers to make concessions, the former education secretary warned: “Can I tell him – we are deadly serious.”
Her threat came after the Government confirmed that the legislation seeking to smooth the UK’s exit from the EU will return to the Commons on November 14.
It explained there would be detailed discussions and a series of crunch votes on dozens of amendments tabled by MPs and peers.
Mr Davis has faced renewed pressure from MPs this week to guarantee parliamentary votes on any deal agreed between the Government and the EU.
Summoned to the Commons yesterday to answer an urgent question from Labour on the issue, he promised that MPs would get a vote on a “draft deal”.
But he repeated his earlier warning that ratification of the final deal may be delayed until after the formal Brexit date in March 2019 if Brussels negotiators drag out the final wrangling to the last possible moment.
“This vote cannot happen until there’s a deal to vote upon,” he said.
“But we are working to reach an agreement on the final deal in good time before we leave in March 2019. Clearly, we cannot say for certain when this will be agreed.”
But he added: “There can be no doubt. Parliament will be involved throughout this process.”
However Mrs Morgan, a leading figure for Remain throughout last year’s EU referendum campaign, insisted that the best way for ministers to ensure MPs and peers get a vote on an exit deal was to accept her proposed amendment to the EU Withdrawal Bill legally guaranteeing parliamentary approval.